I too am waiting on my x4. This is my syma x1. I have a friend that has the X4. It is Very Very Small but is MUCH MUCH more stable due to its 6 axis gyro vs 3 or 4 that the syma has. I think its the acceleromitors that's in the hubsan that make it such a humming bird.
As far a weight and batteries go. The led's and wire wight virtually nothing. And the battery, I would rather keep more small batteries and have the x4 last less time then have the extra weight. More weight makes it less fun to fly ion my opinion. Even at 8 minutes I can keep 6 batteries and my quick charger (imax b6 clone) and keep it in the air for ever.
i got a few of these in the mail form hobbyking, I should get them by the end of next month maybe march...
I would go and find some simple led's and play with them... if you find them at around 3.6v you can directly wire them no need for resistors... Once you light a led up you will see how easy it is to make your quad a flying light ball